This invention concerns an improved apparatus that is useful, primarily, for determining fuel octane numbers.
Known apparatuses for determining fuel octane numbers require long running times and long fuel changing times. Long fuel chaning times are necessary to insure test engine operation on a bubble-free fuel uncontaminated by residues from preceding fuels. Fuels for testing are normally fed through lines and valves with low fuel holdups. The lines and valves acquire air from draining fuels used in a prior fuel testing series. The air forms bubbles in the new fuels of the current testing series and causes a delay in the flow response to demand for a bubble-free fuel. Further, bubbles often form in the fuels during standing between their usages in operating the test engine. The delayed flow responses make octane number determinations relying on automated systems unreliable unless extra operating times are allowed and the total testing times are made unduly long.
Engine drift, another problem associated with known apparatuses, makes the determination of octane numbers subject to error during long running times. Engine drift occurs when a knock test engine run on a particular fuel under constant running and measuring conditions generates knock intensity signals which go through intensity changes. Such changes are cuased by deposit build-up and flaking in the engine, changes in operating temperature, changes in voltage supplied to the knock measuring equipment and mechanical shifts in the engine. Because of the engine drift multiple comparisons are often made to obtain reliable octane numbers. This procedure is expensive.
The improvement in the apparatus of this invention allows the quick, accurate and reliable determination of octane numbers. Virtually eliminated are inaccuracies due to fuel-holdup caused by trapped gas, and unmonitored fuel leakage into the spill chamber after the control valve has been turned off.
The apparatus of this invention is useful for the comparison of a multiplicity of fuels, up to 16 or more. Comparison of such a large number of fuels was impossible heretofore; it is possible now primarily because of the disclosed nozzle placement scheme, i.e. relative location and angle vis-a-vis the spill chamber. The apparatus of this invention is also characterized in that it can be quickly and completely emptied after each series of octane number determinations.
The described advantages are especially valuable in an automated system for determining octane numbers where an operator is not available at all times to assure proper feed, etc. and fuel holdup could result in low or no knock in the test engine and give a false indication of high octane fuel.